The disclosed embodiments of the present invention relate to video coding, and more particularly, to methods for processing 2N×2N block with N being a positive integer greater than four under an intra-prediction mode and related processing circuits thereof.
A prediction block for a current macroblock/block is created from image samples that have already been encoded. This prediction block is subtracted from the current macroblock/block and the result of the subtraction (i.e., the residue data) is compressed and transmitted to the decoder, together with information required for the decoder to repeat the prediction process. The decoder creates an identical prediction block and adds this to the decoded residue data. Regarding an intra-prediction in H.264, the conventional 4×4/8×8 intra-prediction mode has nine prediction modes, including a vertical prediction mode (Mode 0), a horizontal prediction mode (Mode 1), a DC prediction mode (Mode 2), a diagonal_down_left prediction mode (Mode 3), a diagonal_down_right prediction mode (Mode 4), a vertical_right prediction mode (Mode 5), a horizontal_down prediction mode (Mode 6), a vertical_left prediction mode (Mode 7), and a horizontal_up prediction mode (Mode 8).
However, regarding the conventional 16×16 intra-prediction mode in H.264, it has only four prediction modes, including a vertical prediction mode (Mode 0), a horizontal prediction mode (Mode 1), a DC prediction mode (Mode 2), and a plane prediction mode (Mode 3). In addition, regarding the intra-prediction for a 16×16 block, the prediction mode information is coded with the coded block pattern (cbp) information together in the macroblock type (mb_type) syntax element, and no matter whether cbp is 0 or not, a delta quantization parameter (delta QP) must be transmitted. Moreover, a de-blocking filtering operation is performed upon each 4×4 block edge. Thus, when processing certain image contents, the conventional 16×16 intra-prediction mode may not achieve optimized coding efficiency and image quality.